let isdone: boolean = false

let age: number = 2

let binaryNumber: number = 0b1111

let message: string = `hello ${binaryNumber}`

let u: undefined = undefined
let n: null = null

let num: number = 111

let input: any = '111'

let numberOrstring: number | string = '1'

let arrofnumber: number[] = [1, 2]

function test() {
    console.log(arguments)
    arguments.length;
}

// 元组
let user: [string, number] = ['2', 1]
